Systems And Methods For Delivering Fluid To A Wound Therapy Dressing

ABSTRACT

Provided are systems and methods for delivery of fluid to a wound therapy dressing. In exemplary embodiments, a pressure source provides negative pressure to a wound dressing and a biasing mechanism provides positive pressure to a fluid reservoir.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Non-Provisional ApplicationNo. 14/656,458, filed Mar. 12, 2015, entitled “SYSTEMS AND METHODS OFDELIVERING FLUID TO A WOUND THERAPY DRESSING” which claims priority toU.S. Non-provisional patent Ser. No. 13/752,180 filed Jan. 28, 2013,which has been issued as U.S. Pat. No. 8,992,494, entitled “SYSTEMS ANDMETHODS FOR DELIVERING FLUID TO A WOUND THERAPY DRESSING,” which claimspriority to U.S. Provisional Patent Application No. 61/594,033 filedFeb. 2, 2012, entitled SYSTEMS AND METHODS FOR DELIVERING FLUID TO AWOUND THERAPY DRESSING, all of which are incorporated herein byreference for all purposes.

BACKGROUND Field

The subject matter of his specification relates generally to healing ofwounds and wound-treatment therapies. More particularly, but not by wayof limitation, the subject matter relates to systems and methods forimproving fluid-instillation and negative pressure wound therapy (NPWT)apparatuses and methods.

Discussion

Clinical studies and practice have shown that providing a reducedpressure in proximity to a tissue site augments and accelerates thegrowth of new tissue at the tissue site. The applications of thisphenomenon are numerous, but application of reduced pressure has beenparticularly successful in treating wounds. This treatment (frequentlyreferred to in the medical community as “negative pressure woundtherapy,” “reduced pressure therapy,” or “vacuum therapy”) provides anumber of benefits, including faster healing and increased formulationof granulation tissue. Typically, reduced pressure is applied to tissuethrough a porous pad or other manifold device. The porous pad containscells or pores that are capable of distributing reduced pressure to thetissue and channeling fluids that are drawn from the tissue. The porouspad may be incorporated into a dressing having other components thatfacilitate treatment.

Typical instillation therapy instills fluid into a wound under a lowpositive pressure. For maximum therapeutic effect, the instilled fluidshould reach all exposed tissue surfaces. The practice of fully fillinga wound with instillation fluid, combined with the application of porouswound fillers and negative pressure to help distribute fluid, aretechniques used to try and achieve good instillation therapy. Suchtechniques include numerous disadvantages, including difficulty indelivering the desired volume of fluid without overfilling the systemand causing leakage.

Large volumes of fluid may be involved in certain systems, requiringfrequent canister changes that may lead to user dissatisfaction.Although low positive pressures are typically used to fill the woundcavity, the hydraulic (essentially incompressible) nature of the fluidmeans that over filling can quickly cause leakage. Tortuous contourswithin a wound cavity may be difficult to reach with both foam dressingsand liquid-fill techniques as gas pockets may be created. Applying a lowvacuum during liquid instillation (to help maintain a seal and reduceleaking, to minimize patient discomfort, and to aid fluid distribution)can be problematic as instilled fluid may be removed before it is fullydistributed through the dressing. Furthermore, the complexity of thesystem is increased when separate pumping mechanisms are incorporatedinto the wound therapy system.

The referenced shortcomings are not intended to be exhaustive, butrather are among many that tend to impair the effectiveness ofpreviously known techniques in fluid delivery to wound dressings;however, those mentioned here are sufficient to demonstrate that themethodologies appearing in the art have not been satisfactory and that asignificant need exists for the techniques described and claimed in thisdisclosure. For at least the reasons described above, improved woundtreatment systems and methods are therefore desired.

SUMMARY

From the foregoing discussion, it should be apparent that a need existsfor a system and method for improved delivery of fluid to a woundtherapy dressing. The method in the disclosed embodiments substantiallyincludes the steps necessary to carry out the functions presented abovewith respect to the operation of the described system.

Certain embodiments comprise a system configured for delivering fluid toa negative pressure wound therapy dressing, wherein the system comprisesa biasing mechanism configured to compress a fluid reservoir. Inparticular embodiments, the system comprises a housing configured toreceive a fluid reservoir. In specific embodiments, the biasingmechanism is configured to secure a fluid reservoir within the housing.In certain embodiments, the biasing mechanism is configured as a spring.In particular embodiments the spring is a constant-force spring. Incertain embodiments, the positive pressure exerted on the fluid in thereservoir is greater than or equal to approximately 75 mm Hg.

In particular embodiments, the fluid reservoir is a polyethylene bag.Specific embodiments comprise a control circuit configured to control aflow of fluid from the fluid reservoir. In certain embodiments, thecontrol circuit is coupled to a flow sensor configured to detect theflow rate of fluid from the fluid reservoir and to provide a fluid flowrate signal to the control circuit. In particular embodiments, thecontrol circuit is coupled to a flow controller. The flow controller maybe adapted to be positioned in fluid communication between the fluidreservoir and the wound therapy dressing. In specific embodiments, theflow controller is configured as a control valve. Certain embodimentsalso comprise a conduit in fluid communication with a wound dressing.Particular embodiments also comprise a negative pressure source in fluidcommunication with the wound dressing. In specific embodiments, thebiasing mechanism is disposed within a receptacle configured to extendfrom a housing.

Certain embodiments also include a method of delivering a fluid to awound dressing. The method comprises exerting a force from a biasingmechanism on a fluid reservoir and compressing the fluid reservoir,wherein a fluid is directed from the fluid reservoir to the wounddressing via a conduit. Specific embodiments further comprisecontrolling a flow of fluid from the fluid reservoir via a flowcontroller. In particular embodiments, the flow controller is controlledby a control circuit. In certain embodiments, the biasing mechanism is aspring. Particular embodiments also comprise securing the fluidreservoir within a housing via the biasing mechanism. Exerting the threefrom the biasing mechanism may create a positive pressure on the fluidin the reservoir that is, for example, greater than or equal toapproximately 75 mm Hg. Certain embodiments also comprise providing anegative pressure to the wound dressing.

Particular embodiments also include a method of providing instillationfluid and negative pressure to a wound dressing. The method comprises:applying negative pressure to the wound dressing while inhibitinginstillation fluid flow to the wound dressing; ceasing to apply negativepressure to the wound dressing and measuring a volumetric leak rate fromthe wound dressing; enabling instillation fluid flow to the wounddressing; measuring the flow rate of the instillation fluid and thepressure at the wound dressing; verifying wound dressing pressure isapproximately atmospheric pressure; ceasing the flow of instillationfluid to the wound dressing; allowing the instillation fluid to remainin the wound dressing; and removing the instillation fluid from thewound dressing.

In particular embodiments, enabling instillation fluid flow to the wounddressing comprises creating a pressure in a fluid reservoir by exertinga force from a biasing mechanism. In certain embodiments, the biasingmechanism is a spring.

Specific embodiments also include a system for treating a wound with awound dressing. The system comprises: a housing with a receptacleconfigured to receive a fluid reservoir; a biasing mechanism disposedwithin the receptacle for compressing the fluid reservoir; a negativepressure source disposed within the housing; and a conduit for fluidlyconnecting the reservoir, the negative pressure source, and the wounddressing. In particular embodiments, the biasing mechanism is a spring.In certain embodiments, the negative pressure source comprises a vacuumpump and a negative pressure controller. The vacuum pump and thenegative pressure controller may be adapted to be controlled by acontrol circuit according to a negative pressure input signal receivedfrom the wound therapy dressing. In particular embodiments, thereceptacle is slideably received within the housing and configured toextend from the housing. Certain embodiments also comprise a flow sensorand a flow controller coupled to the conduit. The flow sensor and theflow controller may be adapted to be positioned in fluid communicationbetween the fluid reservoir and the wound therapy dressing.

In yet another embodiment, provided is a system adapted to deliver fluidto a wound therapy dressing including a negative pressure source, ahousing, a biasing mechanism, and a control circuit. The negativepressure source is adapted to be in fluid communication with the woundtherapy dressing to provide negative pressure to the wound therapydressing. The housing is adapted to receive a fluid reservoir, the fluidreservoir adapted to be in fluid communication with the wound therapydressing to provide fluid from the fluid reservoir to the wound therapydressing. The biasing mechanism is adapted to secure the fluid reservoirin the housing and to exert a positive pressure on the fluid in thefluid reservoir. The control circuit is adapted to control the negativepressure in the wound therapy dressing.

In yet another embodiment, provided is a system adapted to deliver fluidto a wound therapy dressing including a negative pressure source, ahousing, a flow sensor, a flow controller, and a control circuit. Thenegative pressure source is adapted to be m fluid communication with thewound therapy dressing to provide negative pressure to the wound therapydressing. The housing is adapted to receive a fluid reservoir, the fluidreservoir adapted to be in fluid communication with the wound therapydressing to provide fluid from the fluid reservoir to the wound therapydressing. The flow sensor is adapted to be positioned in fluidcommunication between the fluid reservoir and the wound therapy dressingand to detect a flow rate of the fluid from the fluid reservoir to thewound therapy dressing. The flow controller is adapted to be positionedin fluid communication between the fluid reservoir and the wound therapydressing and to control a flow of the fluid from the fluid reservoir tothe wound therapy dressing. The control circuit is adapted to controlthe negative pressure source. Additionally, the control circuit isadapted to receive a fluid flow rate signal from the flow sensor thatcorresponds to the flow rate of the fluid from the fluid reservoir and anegative pressure signal that corresponds to the negative pressure inthe wound therapy dressing.

In yet another embodiment, disclosed is a method of providinginstillation fluid and negative pressure to a wound dressing including:applying negative pressure to the wound dressing; ceasing to applynegative pressure to the wound dressing when the negative pressure inthe wound dressing reaches a target negative pressure; measuring avolumetric leak rate of the negative pressure from the wound dressing;enabling instillation fluid flow to the wound dressing after the wounddressing reaches the target negative pressure, wherein the instillationfluid flow to the wound dressing is substantially inhibited prior to thenegative pressure in the wound dressing reaching the target negativepressure and the volumetric leak rate being measured; measuring a flowrate of the instillation fluid to the wound dressing; monitoring thenegative pressure in the wound dressing as the instillation fluid flowsinto the wound dressing; ceasing the instillation fluid flow to thewound dressing when the negative pressure in the wound dressing isapproximately atmospheric pressure; allowing the instillation fluid toremain in the wound dressing for a predetermined time period; andremoving the instillation the wound dressing after the predeterminedtime period.

In yet another embodiment, disclosed is a method of providinginstillation fluid and negative pressure to a wound dressing includingapplying negative pressure to the wound dressing until the negativepressure in the wound dressing reaches a target negative pressure;determining a required volumetric flow rate of the negative pressure tothe wound dressing to maintain the negative pressure in the wounddressing substantially at the target negative pressure, the requiredvolumetric flow rate of the negative pressure substantiallycorresponding to a volumetric leak rate of the negative pressure fromthe wound dressing; enabling instillation fluid flow to the wounddressing after the wound dressing reaches the target negative pressure;monitoring the negative pressure in the wound dressing as theinstillation fluid flows into the wound dressing; applying negativepressure to the wound dressing while the instillation fluid flows intothe wound dressing, wherein a flow rate of the negative pressure appliedwhile the instillation fluid flows substantially corresponds to thevolumetric leak rate of the negative pressure from the wound dressing;and ceasing the instillation fluid flow to the wound dressing when thenegative pressure in the wound dressing is approximately atmosphericpressure.

Other features and associated advantages will become apparent withreference to the following detailed description of specific embodimentsin connection with the accompanying drawings.

The term “coupled” is defined as connected, although not necessarilydirectly, and not necessarily mechanically.

The terns “a” and “an” are defined as one or more less this disclosureexplicitly requires otherwise.

The term “substantially” and its variations are defined as being largelybut not necessarily wholly what is specified as understood by one ofordinary skill in the art, and in one non-limiting embodiment“substantially” refers to ranges within 10%, preferably within 5%, morepreferably within 1%, and most preferably within 0.5% of what isspecified.

The terms “comprise” any form of comprise, such as “comprises” and“comprising”), “have” (and any form of have, such as “has” and“having”), “include” (and any form of include, such as “includes” and“including”) and “contain” (and any form of contain, such as “contains”and “containing”) are open-ended linking verbs. As a result, a method ordevice that “comprises,” “has,” “includes” or “contains” one or moresteps or elements possesses those one or more steps or elements, but isnot limited to possessing only those one or more elements. Likewise, astep of a method or an element of a device that “comprises,” “has,”“includes” or “contains” one or more features possesses those one ormore features, but is not limited to possessing only those one or morefeatures. Furthermore, a device or structure that is configured in acertain way is configured in at least that way, but may also beconfigured in ways that are not listed.

The term “negative pressure” refers to an absolute pressure that islower than the absolute atmospheric pressure at the location of use ofthe device. A stated level of negative pressure in a region is thereforea relative measure between the absolute atmospheric pressure and theabsolute pressure in the region. A statement that the negative pressureis decreasing means the pressure in the region is moving towardsatmospheric pressure (i.e. the absolute pressure is increasing). Wherenumeric values are used a negative sign is placed in front of thenumeric pressure value to indicate the value is a negative pressurerelative to atmospheric pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of exemplary embodimentsof the subject matter described herein.

FIG. 1 is a schematic diagram illustrating one embodiment of a systemfor delivering fluid to a wound therapy dressing.

FIG. 2 is a section view of the embodiment of FIG. 1.

FIG. 3 is a schematic diagram illustrating the embodiment of FIG. 1during insertion of a fluid reservoir.

FIG. 4 is schematic flowchart diagram illustrating one embodiment of amethod for delivering fluid to a wound therapy dressing.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Various features and advantageous details are explained more fully withreference to the non-limiting embodiments that are illustrated in theaccompanying drawings and detailed in the following description. Forbrevity, descriptions of well known starting materials, processingtechniques, components, and equipment may be omitted. It should beunderstood, however, that the detailed description, the specificexamples, and embodiments are given by way of illustration only, and notby way of limitation. Various substitutions, modifications, additions,and/or rearrangements within the scope of this specification will becomeapparent to those skilled in the art.

FIGS. 1-3 illustrate an exemplary embodiment of a system 100 forproviding fluid delivery to a wound therapy dressing. As shown, system100 includes a housing 105 with a receptacle 130 configured to receive areservoir 110. In this embodiment, system 100 further comprises aconduit 125 and a wound dressing 120. Conduit 125 may be, for example, amuli-lumen conduit including more than one individual lumen or tube (notshown) housed within conduit 125. The individual lumens or tubes withinconduit 125 may be in fluid communication with wound dressing 120. Eachlumen or tube may be utilized for a different purpose, such as, forexample, instillation of fluid to wound dressing 120 communication ofnegative pressure to wound dressing 120, and receipt of negativepressure feedback from wound dressing 120 as described further below.Reservoir 110 may be, for example, configured as a polyethylene bagsimilar to those used for intravenous fluid delivery. Compression ofreservoir 110 can exert a positive pressure on fluid in reservoir 110and force the fluid from reservoir 110 as described in more detailbelow.

As shown in FIG. 2, receptacle 130 comprises a biasing mechanism 136configured to securely position reservoir 110. In addition, biasingmechanism 136 is configured to compress reservoir 110 by exerting anexternal force on reservoir 110. Continuing with FIG. 2, housing 105 ofsystem 100 may include a negative pressure source 112, a negativepressure controller 113, a control circuit 114, a flow controller 116and a flow sensor 118. Negative pressure source 112 may be, for example,a vacuum pump. Negative pressure controller 113 may be a valve,including for example, a control valve or a manually operated valve.Flow controller 116 may also be configured as a valve, including acontrol valve in certain embodiments,

Referring now to FIG. 3, housing 105 may be configured to receivereservoir 110. As shown in FIG. 3, receptacle 130 may be moved away fromhousing 105 in the direction indicated by arrow 131 for insertion ofreservoir 110 into receptacle 130 in the direction indicated by arrow111. Receptacle 130 can then be moved toward housing 105 (e.g., in thedirection opposite of arrow 131) so that reservoir 110 is received byhousing 105 and in fluid communication with conduit 125, as depicted inFIGS. 1-2. The exemplary embodiment of FIG. 3 depicts receptacle 130slidably received within housing 105 and configured to extend fromhousing 105 in a lateral direction for insertion of reservoir 110 intoreceptacle 130. In another embodiment, receptacle 130 may be configuredto extend from housing 105 in any suitable direction for insertingreservoir 110. In yet another embodiment, receptacle 130 may be coupledto housing 105 and stationary relative to housing 105.

With reservoir 110 in the position shown in FIGS. 1 and 2, system 100 isready for operation. Biasing mechanism 136 is configured to biasreservoir 110 toward housing 105, thereby securing reservoir 110.Extending receptacle 130 from housing 105 as described above reduces thebias from biasing mechanism 136 on reservoir 110 so that a user may moreeasily insert reservoir 110 into receptacle 130. In addition, biasingmechanism 136 is configured to compress reservoir 110, thereby exertinga positive pressure on fluid in reservoir 110. The compression ofreservoir 110 from biasing mechanism 136 exerts a positive pressure onthe fluid in reservoir 110, providing fluid flow from reservoir 110through conduit 125 without the need for an external pumping mechanism(e.g., a peristaltic pump). The ability to provide fluid flow fromreservoir 110 to wound dressing 120 without a separate pumping mechanismcan greatly reduce the complexity of a wound therapy system thatprovides both negative pressure treatment and fluid instillation. Such aconfiguration can also reduce the power requirements associated withfluid delivery.

Biasing mechanism 136 may be configured as a constant-force type springadapted to deliver a substantially constant mechanical load over a fulllength of travel of the spring. The pressure created by biasingmechanism 136 in reservoir 110 may reduce the potential forinconsistencies in fluid flow experienced by system 100 caused by, forexample, height differences between wound dressing 120 and reservoir110. In an exemplary embodiment, biasing mechanism 136 may exert asubstantially constant pressure on reservoir 110 that is greater thanthe pressure required to hold a static column of instillation fluid to aheight approximating the typical distance reservoir 110 may bepositioned below wound dressing 120 during use. For example, biasingmechanism 136 may exert a substantially constant pressure on reservoir110 of approximately 75 mm Hg, corresponding to the pressure required tohold a static column of instillation fluid to a 1 meter height. In otherexemplary embodiments, biasing mechanism 136 may be configured to exertpressure greater than or less than 75 mm Hg.

Referring to FIG. 2, in operation, fluid in conduit 125 is directedthrough flow sensor 118 and flow controller 116. Flow sensor 118 andflow controller 116 are electrically coupled to control circuit 114 andin fluid communication with conduit 125 between fluid reservoir 110 andwound dressing 120. Flow sensor 118 can detect the rate and/or volume offluid flow from reservoir 110 through conduit 125 and provide acorresponding measurement signal, such as a fluid flow rate signal, tocontrol circuit 114. Based on the measurement signal from flow sensor118, control circuit 114 can send a control signal to flow controller116 to control the flow of fluid through conduit 125 to wound dressing120. For example, if the flow rate is detected to be greater thandesired, control circuit 114 can send a signal to flow controller 116 toreduce the amount of fluid flow to wound dressing 120. In oneembodiment, flow controller 116 may be a control valve adapted to reducethe amount of fluid flow by partial or complete closure of the controlvalve. In another embodiment, flow controller 116 may stop fluid flow towound dressing 120 after a particular volume of fluid has been deliveredto wound dressing 120. The volume of fluid may be calculated, forexample, based on the fluid flow rate and the length of time of fluidflow.

Referring now to FIG. 4, a flow chart is provided to illustrate anexemplary method for operating system 100. The order and labeled stepsof the method depicted in FIG. 4 are indicative of one non-limitingembodiment. The format and symbols employed are understood not to limitthe scope of the method, or the order of execution of the steps depictedin the method.

As illustrated in FIG. 4, a method 400 depicted therein includes stepsthat may be executed for the operation of an exemplary system accordingto this disclosure, including system 100 of FIGS. 1-3. Certainembodiments may include a tangible computer readable medium comprisingcomputer readable code that, when executed by a computer, causes thecomputer to perform operations and calculations comprising the stepsdescribed herein and depicted in FIG. 4.

Continuing with FIG. 4, step 401 represents the start of the therapycycle. Step 402 includes bringing system 100 to a target negativepressure (via negative pressure source 112 and negative pressurecontroller 113) while inhibiting the instillation fluid flow (e.g., bymaintaining flow controller 116 in the closed position). Step 403includes turning off negative pressure source 112 and/or closingnegative pressure controller 113 in system 100 when the target negativepressure has been attained in wound dressing 120.

Control circuit 114 may be adapted to control negative pressure source112 for bringing wound dressing 120 up to the target negative pressure,or otherwise regulating the negative pressure in wound dressing 120. Forexample, control circuit 114 may be adapted to receive a negativepressure signal that corresponds to the negative pressure in woundtherapy dressing 120. Control circuit 114 may control the application ofnegative pressure from negative pressure source 112 to wound therapydressing 120 by, for example, sending a signal to negative pressurecontroller 113 and/or negative pressure source 112 to increase ordecrease the negative pressure applied to wound dressing 120 accordingto the negative pressure signal. Control circuit 114 may receive thenegative pressure signal from, for example, a negative pressure feedbacklumen (not shown) in fluid communication with a pressure sensor (notshown) associated with control circuit 114. The negative pressurefeedback lumen may be housed within conduit 125, providing a multi-lumenconfiguration for conduit 125. In other embodiments, the negativepressure feedback lumen stay be coupled to wound dressing 120 separatefrom conduit 125.

The volumetric leak rate of system 100 and wound dressing 120 can becharacterized in step 404, followed by an evaluation of whether thevolumetric leak rate is acceptable in step 405. If the volumetric leakrate is not acceptable, the user can address the cause of the leak ratein step 406 and return to step 402 in the method.

The volumetric leak rate of the negative pressure from wound dressing120 may be substantially equal to a volumetric flow rate of the negativepressure to wound dressing 120 that is required to maintain the negativepressure in wound dressing 120 substantially at the target negativepressure. Thus, the volumetric leak rate may be measured, orcharacterized, by, determining a required volumetric flow rate of thenegative pressure to wound dressing 120 for maintaining the negativepressure in wound dressing 120 substantially at the target negativepressure. The required volumetric flow rate of the negative pressure maybe determined, for example, by successively decreasing the volumetricflow rate of the negative pressure to wound dressing 120 as wounddressing 120 approaches the target negative pressure. The requiredvolumetric flow rate of the negative pressure to wound dressing 120 ismeasured when the volumetric flow rate is decreased to a value thatmaintains wound dressing 120 at the target negative pressure withoutfluctuation of the negative pressure, i.e., a steady state condition. Aprocessor including software that is associated with control circuit 114may be employed to monitor the negative pressure in wound dressing 120and the volumetric flow rate of the negative pressure from negativepressure source 112 as wound dressing 120 reaches the steady statecondition at the target negative pressure.

Once the volumetric leak rate has been determined to be acceptable, auser can again bring the system to the target negative pressure in step407 as previously described for step 402. Negative pressure source 112can then be turned off and/or negative pressure controller 113 closed instep 408, followed by enabling instillation fluid flow in step 409,e.g., by opening a valve in system 100, such as flow controller 116.Biasing mechanism 136 can provide sufficient positive pressure on fluidin fluid reservoir 110 to enable instillation fluid flow in step 409without the use of a separate pumping mechanism as previously described.In addition, instillation fluid flow may be enabled by operation of thenegative pressure in wound dressing 120 drawing fluid from fluidreservoir 110 into wound dressing 120. As fluid from reservoir 110enters wound dressing 120, the negative pressure in wound dressing 120gradually approaches or otherwise returns to atmospheric pressure, i.e.,the negative pressure decreases. In one embodiment, biasing mechanism136 may be omitted.

In step 410, system 100 can monitor the volumetric flow rate of theinstillation fluid, as well as the negative pressure at wound dressing120. The monitored parameters of system 100 can be evaluated in step 411to determine, for example, whether an unexpected change in pressure ispresent, such as the negative pressure at wound dressing 120 returningto atmospheric pressure sooner than expected based on thepreviously-measured volumetric leak rate. If the pressure change is notacceptable, the instillation fluid flow can be discontinued in step 412and operation of system 100 can be terminated in step 413.

If the pressure is changing at an acceptable rate (e.g., due to the flowof instillation fluid from reservoir 110 to wound dressing 120), system100 can verify that the pressure has reached atmospheric pressure instep 414. System 100 may then stop the flow of instillation fluid instep 415 (e.g., by closing flow controller 116 in the instillation fluidflow path) and allow the wound to soak for a predetermined time period.The predetermined time period may be any suitable time period determinedby a clinician as appropriate for the circumstances. In step 416, system100 can store the instilled volume for clinical reference and monitorthe wound reduction. The wound reduction, or healing of the wound, mayreduce the total volume of fluid instilled into wound dressing 120 bythe method described above.

In one embodiment (not shown), the method may include the step ofapplying negative pressure to wound dressing 120 while the fluid fromreservoir 110 flows into wound dressing 120. The flow rate of thenegative pressure applied while the fluid flows into wound dressing 120may substantially correspond to the previously-measured volumetric leakrate of the negative pressure from wound dressing 120. In this manner,system 100 can enhance the accuracy of the volume of the fluid fromreservoir 110 drawn into wound dressing 120 by operation of the negativepressure in wound dressing 120, i.e., the decreasing negative pressurein wound dressing 120 corresponds substantially to the fluid fromreservoir 120 being instilled into wound dressing 120 rather thanleakage of the negative pressure from wound dressing 120.

System 100 can then determine if the soak time is complete in step 417.If the soak time is not complete, system 100 can continue to soak thewound as described in step 415. If the soak time is determined to becomplete, system 100 can recover fluid in step 418 (e.g. by operatingthe negative pressure source 112 and opening negative pressurecontroller 113 to apply negative pressure to wound dressing 120). Thecycle can then be completed in step 419 and system 100 can be poweredoff.

In one embodiment (not shown), the method may include determining atotal volume of the fluid flow from reservoir 110 into wound dressing120. The total volume of the fluid flow may substantially correspond tothe flow rate of the fluid into wound dressing 120 and a time periodrequired for wound dressing 120 to reach approximately atmosphericpressure after enabling the fluid flow to wound dressing 120. As themethod described above is utilized during various stages of healing of aparticular wound, variations in the total volume of fluid instilled intowound dressing 120 may be logged and compared to one another to indicatea rate of healing or reduction for the particular wound.

While the apparatus and methods herein have been described in terms ofpreferred embodiments, it will be apparent to those of skill in the artthat variations may be applied without departing from the scope of thisspecification as defined by the appended claims.

1-29. (canceled)
 30. A system adapted to deliver fluid to a woundtherapy dressing, comprising: a negative pressure source adapted to bein fluid communication with the wound therapy dressing to providenegative pressure to the wound therapy dressing; a housing adapted toreceive a fluid reservoir, the fluid reservoir adapted to be in fluidcommunication with the wound therapy dressing to provide fluid from thefluid reservoir to the wound therapy dressing; a flow sensor adapted tobe positioned in fluid communication between the fluid reservoir and thewound therapy dressing and to detect a flow rate of the fluid from thefluid reservoir to the wound therapy dressing; a flow controller adaptedto be positioned in fluid communication between the fluid reservoir andthe wound therapy dressing and to control a flow of the fluid from thefluid reservoir to the wound therapy dressing; and a control circuitadapted to control the negative pressure source and the flow controller,the control circuit further adapted to receive a fluid flow rate signalfrom the flow sensor that corresponds to the flow rate of the fluid fromthe fluid reservoir and a negative pressure signal that corresponds tothe negative pressure in the wound therapy dressing.
 31. The system ofclaim 30, wherein the fluid reservoir is a polyethylene bag.
 32. Thesystem of claim 30, wherein the flow controller is a control valveadapted to be controlled by the control circuit.
 33. The system of claim30, further comprising a biasing mechanism adapted to exert a positivepressure on the fluid in the fluid reservoir, wherein the biasingmechanism is a constant-force spring.
 34. The system of claim 33,wherein the biasing mechanism is disposed within a receptacle to securethe fluid reservoir in the housing, the receptacle slidably receivedwithin the housing and configured to extend from the housing.
 35. Thesystem of claim 33, wherein the positive pressure on the fluid in thefluid reservoir is at least approximately 75 mm Hg.
 36. The system ofclaim 30, wherein the negative pressure source comprises a vacuum pumpand a negative pressure controller, the control circuit adapted tocontrol the vacuum pump and the negative pressure controller accordingto the negative pressure signal.
 37. The system of claim 30, wherein thenegative pressure source is disposed within the housing.
 38. The systemof claim 36, wherein the negative pressure controller is a controlvalve.
 39. The system of claim 30, further comprising a pressure sensoradapted to measure the negative pressure in the wound therapy dressing.40. A method of providing instillation fluid and negative pressure to awound dressing, comprising: applying negative pressure to the wounddressing until the negative pressure in the wound dressing reaches atarget negative pressure; determining a required volumetric flow rate ofthe negative pressure to the wound dressing to maintain the negativepressure in the wound dressing substantially at the target negativepressure, the required volumetric flow rate of the negative pressuresubstantially corresponding to a volumetric leak rate of the negativepressure from the wound dressing; enabling instillation fluid flow tothe wound dressing after the wound dressing reaches the target negativepressure; monitoring the negative pressure in the wound dressing as theinstillation fluid flows into the wound dressing; applying negativepressure to the wound dressing while the instillation fluid flows intothe wound dressing, wherein a flow rate of the negative pressure appliedwhile the instillation fluid flows substantially corresponds to thevolumetric leak rate of the negative pressure from the wound dressing;and ceasing the instillation fluid flow to the wound dressing when thenegative pressure in the wound dressing is approximately atmosphericpressure.
 41. The method of claim 40, wherein enabling instillationfluid flow to the wound dressing comprises exerting a force oninstillation fluid in a fluid reservoir with a biasing mechanism andpermitting the negative pressure in the wound dressing to draw theinstillation fluid into the wound dressing, the fluid reservoir being influid communication with the wound dressing, wherein the instillationfluid flow to the wound dressing is substantially inhibited prior to thenegative pressure in the wound dressing reaching the target negativepressure.
 42. The method of claim 40, further comprising determining atotal volume of the instillation fluid flow to the wound dressing, thetotal volume of the instillation fluid flow substantially correspondingto a flow rate of the instillation fluid to the wound dressing and atime period required for the wound dressing to reach approximatelyatmospheric pressure after enabling the instillation fluid flow to thewound dressing.
 43. A system adapted to deliver fluid to a wound therapydressing, comprising: a housing adapted to receive a fluid reservoir,the fluid reservoir adapted to be in fluid communication with the woundtherapy dressing to provide fluid from the fluid reservoir to the woundtherapy dressing; a mechanism adapted to apply a positive pressure tothe fluid reservoir; a control circuit adapted to control the deliveryof negative pressure and delivery of the fluid to the wound therapydressing; and a flow sensor adapted to be positioned in fluidcommunication between the fluid reservoir and the wound therapy dressingand to detect a flow rate of the fluid from the fluid reservoir to thewound therapy dressing; wherein the control circuit is further adaptedto receive a fluid flow rate signal from the flow sensor thatcorresponds to the flow rate of the fluid from the fluid reservoir. 44.The system of claim 43, wherein the mechanism comprises a biasingmechanism.
 45. The system of claim 43, further comprising a flowcontroller adapted to be positioned in fluid communication between thefluid reservoir and the wound therapy dressing.
 46. The system of claim43, wherein the housing further comprises a receptacle configured toreceive the fluid reservoir.
 47. The system of claim 46, wherein thereceptacle is further configured to extend away from the housing toreceive the fluid reservoir.